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Modeling the light-induced electric potential difference (ΔΨ), the pH difference (ΔpH) and the proton motive force across the thylakoid membrane in C3 leaves. J Theor Biol 2017; 413:11-23. [DOI: 10.1016/j.jtbi.2016.10.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 10/07/2016] [Accepted: 10/28/2016] [Indexed: 01/18/2023]
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Lyu H, Lazár D. Modeling the light-induced electric potential difference ΔΨ across the thylakoid membrane based on the transition state rate theory. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1858:239-248. [PMID: 28027878 DOI: 10.1016/j.bbabio.2016.12.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 12/01/2016] [Accepted: 12/23/2016] [Indexed: 01/10/2023]
Abstract
In photosynthesis, electron transport-coupled proton movement initiates the formation of the light-induced electric potential difference, ΔΨ, across the thylakoid membrane (TM). Ions are transported across the TM to counterbalance the charge of protons accumulated in the lumen. The objective of this work is to construct range of mathematical models for simulation of ΔΨ, using the transition state rate theory (TSRT) for description of movement of ions through the channels. The TSRT considers either single-ion (TSRT-SI) or multi-ion occupancy (TSRT-MI) in the channels. Movement of ions through the channel pore is described by means of energy barriers and binding sites; ions move in and out of vacant sites with rate constants that depend on the barrier heights and well depths, as well as on the interionic repulsion in TSRT-MI model. Three energy motifs are used to describe the TSRT-SI model: two-barrier one-site (2B1S), three-barrier two-site (3B2S), and four-barrier three-site (4B3S). The 3B2S energy motif is used for the TSRT-MI model. The accumulation of cations due to the TM surface negative fixed charges is also taken into account. A model employing the electro-diffusion theory instead of the TSRT is constructed for comparison. The dual wavelength transmittance signal (ΔA515-560nm) measuring the electrochromic shift (ECS) provides a proxy for experimental light-induced ΔΨ. The simulated ΔΨ traces qualitatively agree with the measured ECS traces. The models can simulate different channel conducting regimes and assess their impact on ΔΨ. The ionic flux coupling in the TSRT-MI model suggests that an increase in the internal or external K+ concentration may block the outward or the inward Mg2+ current, respectively.
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Affiliation(s)
- Hui Lyu
- Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Dušan Lazár
- Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic.
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Schroeder TBH, Leriche G, Koyanagi T, Johnson MA, Haengel KN, Eggenberger OM, Wang CL, Kim YH, Diraviyam K, Sept D, Yang J, Mayer M. Effects of Lipid Tethering in Extremophile-Inspired Membranes on H(+)/OH(-) Flux at Room Temperature. Biophys J 2016; 110:2430-2440. [PMID: 27276261 PMCID: PMC4906265 DOI: 10.1016/j.bpj.2016.04.044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 04/08/2016] [Accepted: 04/12/2016] [Indexed: 01/22/2023] Open
Abstract
This work explores the proton/hydroxide permeability (PH+/OH-) of membranes that were made of synthetic extremophile-inspired phospholipids with systematically varied structural elements. A fluorescence-based permeability assay was optimized to determine the effects on the PH+/OH- through liposome membranes with variations in the following lipid attributes: transmembrane tethering, tether length, and the presence of isoprenoid methyl groups on one or both lipid tails. All permeability assays were performed in the presence of a low concentration of valinomycin (10 nM) to prevent buildup of a membrane potential without artificially increasing the measured PH+/OH-. Surprisingly, the presence of a transmembrane tether did not impact PH+/OH- at room temperature. Among tethered lipid monolayers, PH+/OH- increased with increasing tether length if the number of carbons in the untethered acyl tail was constant. Untethered lipids with two isoprenoid methyl tails led to lower PH+/OH- values than lipids with only one or no isoprenoid tails. Molecular dynamics simulations revealed a strong positive correlation between the probability of observing water molecules in the hydrophobic core of these lipid membranes and their proton permeability. We propose that water penetration as revealed by molecular dynamics may provide a general strategy for predicting proton permeability through various lipid membranes without the need for experimentation.
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Affiliation(s)
- Thomas B H Schroeder
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan; Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland
| | - Geoffray Leriche
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Takaoki Koyanagi
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Mitchell A Johnson
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Kathryn N Haengel
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Olivia M Eggenberger
- Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Claire L Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Young Hun Kim
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Karthik Diraviyam
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - David Sept
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Jerry Yang
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California
| | - Michael Mayer
- Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan.
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Lee EH, Lee SW, Saraf RF. Noninvasive measurement of membrane potential modulation in microorganisms: photosynthesis in green algae. ACS NANO 2014; 8:780-6. [PMID: 24354302 DOI: 10.1021/nn405437z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Cell membrane potential (CMP) modulation is a physical measurement to quantitatively probe cell physiology in real time at high specificity. Electrochemical field effect transistors (eFETs) made from graphene and Si nanowire provide strong mechanical and electrical coupling with neurons and muscle cells to noninvasively measure CMP at high sensitivity. To date, there are no noninvasive methods to study electrophysiology of microorganisms because of stiff cell walls and significantly smaller membrane polarizations. An eFET made from the smallest possible nanostructure, a nanoparticle, with sensitivity to a single-electron charge is developed to noninvasively measure CMP modulation in algae. The applicability of the device is demonstrated by measuring CMP modulation due to a light-induced proton gradient inside the chloroplast during photosynthesis. The ∼9 mV modulation in CMP in algae is consistent with the absorbance spectrum of chlorophyll, photosynthetic pathway, and inorganic carbon source concentration in the environment. The method can potentially become a routine method to noninvasively study electrophysiology of cells, such as microorganisms for biofuels.
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Affiliation(s)
- Eun-Hee Lee
- Chemical and Biomolecular Engineering, University of Nebraska-Lincoln , Lincoln, Nebraska 68588, United States
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Pennisi CP. Molecular photovoltaic structures for optical activation of excitable cells: current advances and perspectives. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:6230-2. [PMID: 21097166 DOI: 10.1109/iembs.2010.5627714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Current neural stimulation devices for the treatment of sensory and motor disorders are based on electrical stimulation. Using this technique, neural activity is triggered by electrical stimuli applied through electrodes in contact with the cells. Due to physical constraints of the electrodes the spatial control of stimulation is limited, which in some cases generates unwanted side effects. In addition, adverse tissue reactions occur after long term contact with the electrodes. A potential solution is the application of methods based on light instead of electrical energy, in which the electrical stimulator and the electrode are replaced by a light source and an optical fiber. Although optical stimulation approaches that allow spatially selective, highly specific and contact-free control of the neural activity have been developed in recent years, their implementation requires genetic manipulation, limiting the perspectives for clinical applications. A molecular photovoltaic structure potentially able to mediate light-induced cellular responses without involving genetic modification is the photosynthetic pigment-protein complex Photosystem I (PSI). In this work, the recent advances on the application of PSI reaction centers for optical control of cellular activity are presented. Perspectives of application of PSI reaction centers in the development of future methods for clinical neural stimulation are also presented.
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Affiliation(s)
- Cristian P Pennisi
- Department of Health Science and Technology, Aalborg University, Denmark.
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